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pair_eam_opt.cpp
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Thu, Jul 4, 01:57

pair_eam_opt.cpp
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/* ----------------------------------------------------------------------
LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
http://lammps.sandia.gov, Sandia National Laboratories
Steve Plimpton, sjplimp@sandia.gov
Copyright (2003) Sandia Corporation. Under the terms of Contract
DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
certain rights in this software. This software is distributed under
the GNU General Public License.
See the README file in the top-level LAMMPS directory.
------------------------------------------------------------------------- */
/* ----------------------------------------------------------------------
Contributing authors:
James Fischer, High Performance Technologies, Inc.
Charles Cornwell, High Performance Technologies, Inc.
David Richie, Stone Ridge Technology
Vincent Natoli, Stone Ridge Technology
------------------------------------------------------------------------- */
#include <math.h>
#include <stdlib.h>
#include "pair_eam_opt.h"
#include "atom.h"
#include "comm.h"
#include "force.h"
#include "neigh_list.h"
#include "memory.h"
using namespace LAMMPS_NS;
/* ---------------------------------------------------------------------- */
PairEAMOpt::PairEAMOpt(LAMMPS *lmp) : PairEAM(lmp) {}
/* ---------------------------------------------------------------------- */
void PairEAMOpt::compute(int eflag, int vflag)
{
if (eflag || vflag) ev_setup(eflag,vflag);
else evflag = vflag_fdotr = eflag_global = eflag_atom = 0;
if (evflag) {
if (eflag) {
if (force->newton_pair) return eval<1,1,1>();
else return eval<1,1,0>();
} else {
if (force->newton_pair) return eval<1,0,1>();
else return eval<1,0,0>();
}
} else {
if (force->newton_pair) return eval<0,0,1>();
else return eval<0,0,0>();
}
}
/* ---------------------------------------------------------------------- */
template < int EVFLAG, int EFLAG, int NEWTON_PAIR >
void PairEAMOpt::eval()
{
typedef struct { double x,y,z; } vec3_t;
typedef struct {
double rhor0i,rhor1i,rhor2i,rhor3i;
double rhor0j,rhor1j,rhor2j,rhor3j;
} fast_alpha_t;
typedef struct {
double rhor4i,rhor5i,rhor6i;
double rhor4j,rhor5j,rhor6j;
double z2r0,z2r1,z2r2,z2r3,z2r4,z2r5,z2r6;
double _pad[3];
} fast_gamma_t;
int i,j,ii,jj,inum,jnum,itype,jtype;
double evdwl = 0.0;
double* _noalias coeff;
// grow energy array if necessary
if (atom->nmax > nmax) {
memory->sfree(rho);
memory->sfree(fp);
nmax = atom->nmax;
rho = (double *) memory->smalloc(nmax*sizeof(double),"pair:rho");
fp = (double *) memory->smalloc(nmax*sizeof(double),"pair:fp");
}
double** _noalias x = atom->x;
double** _noalias f = atom->f;
int* _noalias type = atom->type;
int nlocal = atom->nlocal;
vec3_t* _noalias xx = (vec3_t*)x[0];
vec3_t* _noalias ff = (vec3_t*)f[0];
double tmp_cutforcesq = cutforcesq;
double tmp_rdr = rdr;
int nr2 = nr-2;
int nr1 = nr-1;
inum = list->inum;
int* _noalias ilist = list->ilist;
int** _noalias firstneigh = list->firstneigh;
int* _noalias numneigh = list->numneigh;
int ntypes = atom->ntypes;
int ntypes2 = ntypes*ntypes;
fast_alpha_t* _noalias fast_alpha =
(fast_alpha_t*) malloc(ntypes2*(nr+1)*sizeof(fast_alpha_t));
for (i = 0; i < ntypes; i++) for (j = 0; j < ntypes; j++) {
fast_alpha_t* _noalias tab = &fast_alpha[i*ntypes*nr+j*nr];
if (type2rhor[i+1][j+1] >= 0) {
for(int m = 1; m <= nr; m++) {
tab[m].rhor0i = rhor_spline[type2rhor[i+1][j+1]][m][6];
tab[m].rhor1i = rhor_spline[type2rhor[i+1][j+1]][m][5];
tab[m].rhor2i = rhor_spline[type2rhor[i+1][j+1]][m][4];
tab[m].rhor3i = rhor_spline[type2rhor[i+1][j+1]][m][3];
}
}
if (type2rhor[j+1][i+1] >= 0) {
for(int m = 1; m <= nr; m++) {
tab[m].rhor0j = rhor_spline[type2rhor[j+1][i+1]][m][6];
tab[m].rhor1j = rhor_spline[type2rhor[j+1][i+1]][m][5];
tab[m].rhor2j = rhor_spline[type2rhor[j+1][i+1]][m][4];
tab[m].rhor3j = rhor_spline[type2rhor[j+1][i+1]][m][3];
}
}
}
fast_alpha_t* _noalias tabeight = fast_alpha;
fast_gamma_t* _noalias fast_gamma =
(fast_gamma_t*) malloc(ntypes2*(nr+1)*sizeof(fast_gamma_t));
for (i = 0; i < ntypes; i++) for (j = 0; j < ntypes; j++) {
fast_gamma_t* _noalias tab = &fast_gamma[i*ntypes*nr+j*nr];
if (type2rhor[i+1][j+1] >= 0) {
for(int m = 1; m <= nr; m++) {
tab[m].rhor4i = rhor_spline[type2rhor[i+1][j+1]][m][2];
tab[m].rhor5i = rhor_spline[type2rhor[i+1][j+1]][m][1];
tab[m].rhor6i = rhor_spline[type2rhor[i+1][j+1]][m][0];
}
}
if (type2rhor[j+1][i+1] >= 0) {
for(int m = 1; m <= nr; m++) {
tab[m].rhor4j = rhor_spline[type2rhor[j+1][i+1]][m][2];
tab[m].rhor5j = rhor_spline[type2rhor[j+1][i+1]][m][1];
tab[m].rhor6j = rhor_spline[type2rhor[j+1][i+1]][m][0];
tab[m].z2r6 = z2r_spline[type2z2r[i+1][j+1]][m][0];
}
}
if (type2z2r[i+1][j+1] >= 0) {
for(int m = 1; m <= nr; m++) {
tab[m].z2r0 = z2r_spline[type2z2r[i+1][j+1]][m][6];
tab[m].z2r1 = z2r_spline[type2z2r[i+1][j+1]][m][5];
tab[m].z2r2 = z2r_spline[type2z2r[i+1][j+1]][m][4];
tab[m].z2r3 = z2r_spline[type2z2r[i+1][j+1]][m][3];
tab[m].z2r4 = z2r_spline[type2z2r[i+1][j+1]][m][2];
tab[m].z2r5 = z2r_spline[type2z2r[i+1][j+1]][m][1];
tab[m].z2r6 = z2r_spline[type2z2r[i+1][j+1]][m][0];
}
}
}
fast_gamma_t* _noalias tabss = fast_gamma;
// zero out density
if (NEWTON_PAIR) {
int m = nlocal + atom->nghost;
for (i = 0; i < m; i++) rho[i] = 0.0;
} else for (i = 0; i < nlocal; i++) rho[i] = 0.0;
// rho = density at each atom
// loop over neighbors of my atoms
// loop over neighbors of my atoms
for (ii = 0; ii < inum; ii++) {
i = ilist[ii];
double xtmp = xx[i].x;
double ytmp = xx[i].y;
double ztmp = xx[i].z;
itype = type[i] - 1;
int* _noalias jlist = firstneigh[i];
jnum = numneigh[i];
double tmprho = rho[i];
fast_alpha_t* _noalias tabeighti = &tabeight[itype*ntypes*nr];
for (jj = 0; jj < jnum; jj++) {
j = jlist[jj];
j &= NEIGHMASK;
double delx = xtmp - xx[j].x;
double dely = ytmp - xx[j].y;
double delz = ztmp - xx[j].z;
double rsq = delx*delx + dely*dely + delz*delz;
if (rsq < tmp_cutforcesq) {
jtype = type[j] - 1;
double p = sqrt(rsq)*tmp_rdr;
if ( (int)p <= nr2 ) {
int m = (int)p + 1;
p -= (double)((int)p);
fast_alpha_t& a = tabeighti[jtype*nr+m];
tmprho += ((a.rhor3j*p+a.rhor2j)*p+a.rhor1j)*p+a.rhor0j;
if (NEWTON_PAIR || j < nlocal) {
rho[j] += ((a.rhor3i*p+a.rhor2i)*p+a.rhor1i)*p+a.rhor0i;
}
} else {
fast_alpha_t& a = tabeighti[jtype*nr+nr1];
tmprho += a.rhor3j+a.rhor2j+a.rhor1j+a.rhor0j;
if (NEWTON_PAIR || j < nlocal) {
rho[j] += a.rhor3i+a.rhor2i+a.rhor1i+a.rhor0i;
}
}
}
}
rho[i] = tmprho;
}
// communicate and sum densities
if (NEWTON_PAIR) comm->reverse_comm_pair(this);
// fp = derivative of embedding energy at each atom
// phi = embedding energy at each atom
// if rho > rhomax (e.g. due to close approach of two atoms),
// will exceed table, so add linear term to conserve energy
for (ii = 0; ii < inum; ii++) {
i = ilist[ii];
double p = rho[i]*rdrho;
int m = MIN((int)p,nrho-2);
p -= (double)m;
++m;
coeff = frho_spline[type2frho[type[i]]][m];
fp[i] = (coeff[0]*p + coeff[1])*p + coeff[2];
if (EFLAG) {
double phi = ((coeff[3]*p + coeff[4])*p + coeff[5])*p + coeff[6];
if (rho[i] > rhomax) phi += fp[i] * (rho[i]-rhomax);
phi *= scale[type[i]][type[i]];
if (eflag_global) eng_vdwl += phi;
if (eflag_atom) eatom[i] += phi;
}
}
// communicate derivative of embedding function
comm->forward_comm_pair(this);
// compute forces on each atom
// loop over neighbors of my atoms
for (ii = 0; ii < inum; ii++) {
i = ilist[ii];
double xtmp = xx[i].x;
double ytmp = xx[i].y;
double ztmp = xx[i].z;
int itype1 = type[i] - 1;
int* _noalias jlist = firstneigh[i];
jnum = numneigh[i];
double tmpfx = 0.0;
double tmpfy = 0.0;
double tmpfz = 0.0;
fast_gamma_t* _noalias tabssi = &tabss[itype1*ntypes*nr];
double* _noalias scale_i = scale[itype1+1]+1;
for (jj = 0; jj < jnum; jj++) {
j = jlist[jj];
j &= NEIGHMASK;
double delx = xtmp - xx[j].x;
double dely = ytmp - xx[j].y;
double delz = ztmp - xx[j].z;
double rsq = delx*delx + dely*dely + delz*delz;
if (rsq < tmp_cutforcesq) {
jtype = type[j] - 1;
double r = sqrt(rsq);
double rhoip,rhojp,z2,z2p;
double p = r*tmp_rdr;
if ( (int)p <= nr2 ) {
int m = (int) p + 1;
p -= (double)((int) p);
fast_gamma_t& a = tabssi[jtype*nr+m];
rhoip = (a.rhor6i*p + a.rhor5i)*p + a.rhor4i;
rhojp = (a.rhor6j*p + a.rhor5j)*p + a.rhor4j;
z2 = ((a.z2r3*p + a.z2r2)*p + a.z2r1)*p + a.z2r0;
z2p = (a.z2r6*p + a.z2r5)*p + a.z2r4;
} else {
fast_gamma_t& a = tabssi[jtype*nr+nr1];
rhoip = a.rhor6i + a.rhor5i + a.rhor4i;
rhojp = a.rhor6j + a.rhor5j + a.rhor4j;
z2 = a.z2r3 + a.z2r2 + a.z2r1 + a.z2r0;
z2p = a.z2r6 + a.z2r5 + a.z2r4;
}
// rhoip = derivative of (density at atom j due to atom i)
// rhojp = derivative of (density at atom i due to atom j)
// phi = pair potential energy
// phip = phi'
// z2 = phi * r
// z2p = (phi * r)' = (phi' r) + phi
// psip needs both fp[i] and fp[j] terms since r_ij appears in two
// terms of embed eng: Fi(sum rho_ij) and Fj(sum rho_ji)
// hence embed' = Fi(sum rho_ij) rhojp + Fj(sum rho_ji) rhoip
// scale factor can be applied by thermodynamic integration
double recip = 1.0/r;
double phi = z2*recip;
double phip = z2p*recip - phi*recip;
double psip = fp[i]*rhojp + fp[j]*rhoip + phip;
double fpair = -scale_i[jtype]*psip*recip;
tmpfx += delx*fpair;
tmpfy += dely*fpair;
tmpfz += delz*fpair;
if (NEWTON_PAIR || j < nlocal) {
ff[j].x -= delx*fpair;
ff[j].y -= dely*fpair;
ff[j].z -= delz*fpair;
}
if (EFLAG) evdwl = scale_i[jtype]*phi;
if (EVFLAG) ev_tally(i,j,nlocal,NEWTON_PAIR,
evdwl,0.0,fpair,delx,dely,delz);
}
}
ff[i].x += tmpfx;
ff[i].y += tmpfy;
ff[i].z += tmpfz;
}
free(fast_alpha); fast_alpha = 0;
free(fast_gamma); fast_gamma = 0;
if (vflag_fdotr) virial_fdotr_compute();
}

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